1. Field of the Invention
This invention relates to a safety seat belt retractor provided with an inertia sensing member capable of sensing a predetermined speed variation or tilting of a vehicle body and capable of assuming a first position of stable state and a second position corresponding to said predetermined speed variation or tilting and being continuously displaceable from said first position to said second position to restrain a seat occupant.
2. Description of the Prior Art
In a lock mechanism for directly sensing a sudden speed variation of a vehicle body due to collision or the like or tilting of the vehicle body on a sloping road or the like and for preventing draw-out of webbing from a safety seat belt retractor to restrain a seat occupant, it is well-known to use an inertia sensing member as the means for sensing the speed variation or tilting of the vehicle body. As such an inertia sensing member, there is well-known the pendulum type which utilizes the swing of a pendulum, the ball type which utilizes the displacement of a ball member, or the upright type in which an inertia member kept upright is caused to fall down. In the case of the upright type inertia sensing member, the critical value at which the inertia member falls down is clear and there is an advantage in that the operating force resulting from the action of falling down is great, whereas in the case of the pendulum type or the ball type sensing member, the swing (namely, displacement) of the pendulum or the displacement of the ball is continuous. These types have a disadvantage in that it is difficult to determine the critical value of their operation and the operating force is smaller, being in inverse proportion to the amount of displacement.